Handle failed requestBuffer after successful dequeueBuffer

If the virtual display consumer disconnects after the
VirtualDisplaySurface dequeues a buffer but before it requests it, the
request will fail. Previously the error was ignored, and the caller
would get a success result but a NULL buffer. Now the dequeued buffer
is cancelled and the error propagated to the caller.

Bug: 14140551
Change-Id: I91547885c2cf6063dc7a8f02d97f2df282cdde2c